Bubble bars or solid bubble bath are very popular, but it requires a different technic to making soap. As a lot of people have problems making them and there is no clear info to be found, it seemed useful to make a photo tutorial.

Now weigh the cream of tartar. Put this also through the strainer (it is quite lumpy) into the bowl.

If you want to add other powdered ingredients you can do so at this point. Mix the dry ingredients well.
Now add the fragrance and mix this through the dry mixture.

Make sure the fragrance is fully incorperated. It might be helpfull to squeeze it with your hands until you do not feel any lumps.

Now put your mask on and very carefully weigh the SLS/SLSA. This is a very fine powder that can irritate your lungs, so keep kids/animals out of the room and air very well.
Add the powder to the mixture.

Fold the mixture very carefully. If you mix too vigorously the dust will send you out of the room coughing your lungs out.

Add your fluid surfactants little by little.

Now put your gloves on and knead the mixture. If it is too dry you add a bit more liquid surfactant, if it is too wet you add a bit of tapioca powder.

You are ready when the mixture forms a ball and your gloves are pretty clean.

Now mix your colourant(s) with a little glycerine. Try to make sure no lumps are left as these will show in your final product.

Divide your mixture in the parts you want to colour. Keep one part in the mixing bowl and set the rest aside.

Now add your colourant and knead with your hands until the colour is solid. If the mixture becomes too sticky, just add some tapioca powder.

Sprinkle some tapioca on the silicone sheet and put one part of the mixture on this.

Now push the mixture down with your fingers to make a flat pancake.

If the top gets sticky, just dust with some tapioca. The thinner the pancake, the easier to roll.

Now add your second layer on top of the first and flatten this one as well.

Now fold the bottom over and push down lightly.

Now fold the bottom of the sheet over a bit further, so more gets rolled.

Continue until the roll is fully rolled up. Now squeeze the roll lightly, so all layers stick together.

Cut the roll in equal parts.

You can see the rolled layers here.

Take each piece and hand form it to your liking. I made every piece round and lightly pushed it down.

Now let the bubble pieces dry for at least 24 hours before packaging. They should feel hard to the touch.

To use them you crumble one under warm running water. Now slide into the bath and enjoy your luxurious bubbles!